The present disclosure relates to continuous feed printers, and more particularly, to a portable label or thermal printer having a selectively adjustable, asymmetrically damped media centering assembly.
Portable or desktop printers are often used in commercial settings, e.g., in warehouses, in industrial and manufacturing environments, by shipping services, in vending machine routes, in the vending and gaming industries, and in retail establishments for ticket printing and inventory control. Ideally, portable printers weigh only a few pounds and are small enough to be easily carried during use and/or easily attached to a buckle or a harness-type device. This enables the user to print labels or receipts on demand without having to retrieve a printed label from a printing station. Because the printer is portable, the printer may include a power source, such as a disposable or rechargeable battery, and may additionally communicate with a host terminal or network connection via a wireless interface, such as a radio or optical interface. A portable printer may utilize sheet-fed media, or, more popularly, continuous-feed media, e.g., rolls of paper, labels, tags, and the like. Portable printers commonly employ direct thermal transfer techniques, whereby thermochromic media passes over a thermal print head which selectively heats areas of the media to create a visible image. Also popular are thermal transfer printers which employ a heat-sensitive ribbon to transfer images to media.
A continuous feed printer is particularly suitable for printing onto stock material which may include, but is not necessarily limited to, labels, receipts, item labels, shelf labels/tags, ticket stubs, stickers, hang tags, price stickers, and the like. Label printers may incorporate a media supply of “peel away” labels adhered to a coated substrate wound in a rolled configuration. Alternatively, a media supply may include a plain paper roll suitable for ink-based or toner-based printing. Continuous media is typically supplied in rolls, and is available in a wide range of widths. The roll media may be wound around a generally tubular core which supports the roll media. The core may have a standard size, or arbitrarily-sized inner diameter. In use, the media is drawn against a printing head, which, in turn, causes images to be created on the media stock by, e.g., impact printing (dot matrix, belt printing), by localized heating (thermal transfer printing), inkjet printing, toner-based printing, or other suitable printing methods.
Portable or thermal printers may be designed for use with one type of printing media or one particular size of print media, e.g., 2-inch label stock or 3-inch label stock. Other portable printers may be configurable to accommodate different media types and sizes. Such printers may include a media centering mechanism which is designed to accommodate roll media of varying widths and/or core diameters. The media centering mechanism may include opposing support members configured to engage the media roll core. A media centering mechanism typically includes first and second support members that are generally biased towards each other to secure the media roll. Movement of the first and second support members may be synchronized by one or more gears or belts such that, when a support member is moved a distance from the centerline of the media roll, the other support member moves a corresponding distance in the opposing direction from the centerline of the media roll.
Many of the media centering mechanisms associated with portable printers are not particularly versatile or convenient to use, and may employ various spring-loaded elements that are intended to accommodate media of various types and sizes. As a result, even though certain portable printers may accommodate media of various sizes, to load such media a user must manipulate the spring-loaded members and other mechanical elements using both hands. Such spring-loaded elements can suddenly snap into position with considerable force, which may result in an unpleasant user experience, damage to the print media, and even damage to the printer itself.